A Validated Tropical-Extratropical Flood Hazard Assessment for New York Harbor

Area of Science:

• Coastal engineering
• Climate science
• Extreme weather events

Background:

• Previous flood risk studies for New York Harbor (NYH) yielded inconsistent 100-year storm tide results.
• This uncertainty complicated flood mitigation planning post-Hurricane Sandy.

Purpose of the Study:

• To conduct a robust flood hazard assessment for NYH.
• To improve confidence in understanding regional flood potential.
• To differentiate the impacts of tropical cyclones (TCs) and extratropical cyclones (ETCs).

Main Methods:

• Developed a statistical-stochastic model for 606 synthetic North Atlantic TCs.
• Simulated historical ETCs with random tide scenarios.
• Validated modeling against historical observations at multiple stages.

Main Results:

• The 100-year return period storm tide at NYH is estimated at 2.70 m.
• Hurricane Sandy's storm tide (3.38 m) was a 260-year event, the largest since at least 1700.
• TC and ETC flood exceedance curves were consistent with historical data.

Conclusions:

• TCs and ETCs require separate analysis due to distinct meteorological and frequency characteristics.
• This assessment offers a more reliable foundation for flood risk management in NYH.
• Hurricane Sandy's impact was historically unprecedented for the region.